The First Peloponnesian War (460–445 BC) was fought between Sparta as the leaders of the Peloponnesian League and Sparta’s other allies, most notably Thebes, and the Delian League led by Athens with support from Argos. This war consisted of a series of conflicts and minor wars, such as the Second Sacred War. There were several causes for the war including the building of the Athenian long walls, Megara’s defection and the envy and concern felt by Sparta at the growth of the Athenian Empire.

The war began in 460 BC (Battle of Oenoe).[1][2][3][4] At first the Athenians had the better of the fighting, winning the naval engagements using their superior fleet. They also had the better of the fighting on land, until 457 BC when the Spartans and their allies defeated the Athenian army at Tanagra. The Athenians, however, counterattacked and scored a crushing victory over the Boeotians at the Battle of Oenophyta and followed this victory up by conquering all of Boeotia except for Thebes.

Athens further consolidated their position by making Aegina a member of the Delian League and by ravaging the Peloponnese. The Athenians were defeated in 454 BC by the Persians in Egypt which caused them to enter into a five years’ truce with Sparta. However, the war flared up again in 448 BC with the start of the Second Sacred War. In 446 BC, Boeotia revolted and defeated the Athenians at Coronea and regained their independence.

The First Peloponnesian War ended in an arrangement between Sparta and Athens, which was ratified by the Thirty Years’ Peace (winter of 446–445 BC). According to the provisions of this peace treaty, both sides maintained the main parts of their empires. Athens continued its domination of the sea while Sparta dominated the land. Megara returned to the Peloponnesian League and Aegina became a tribute-paying but autonomous member of the Delian League. The war between the two leagues restarted in 431 BC and in 404 BC.